FIELD OF INVENTION
This invention relates to the removal of residual materials such as slag and iron from torpedo cars and the like. Torpedo cars are commonly employed to transport molten pig iron from the blast furnace to steelmaking facilitates such as open hearth furnaces, basic oxygen furnaces, electric furnaces and the like. Typically the contents of torpedo cars are emptied into a refractory lined transfer ladle which is then used to transfer the iron into the steelmaking furnace for refining into steel.
Pig iron normally contains sulphur in amounts that are greater than can be tolerated in the final steel product. Hence, such impurity must be removed during refining into steel. This problem has been magnified due to the increased use of relatively high sulphur containing coke in the blast furnace as well as due to certain operating practices that, while yielding higher productivity have also resulted in higher sulphur contents than obtained in the past. A penalty for such blast furnace practices is encountered during steelmaking because sulphur removal is extremely difficult and time consuming. To overcome such penalty, steel producers have resorted to the use of sulphur removal operations prior to charging of the pig iron into the steelmaking vessel. These desulphurization operations are conducted in the torpedo car at a desulphurization station located between the blast furnace and steelmaking facility. Typically several types of desulphurization operations may be conducted. The usual practice has been to utilize a rotatable angled heat resistant lance to inject desulphurization materials that are conveyed by an inert gas beneath the surface of the molten pig iron. Calcium carbide is utilized in some processes and a lime-magnesium mixture is utilized in other processes of commercial interest. In any event, in either process, sulphur reacts with the injected material and the reaction product floats to the top of the iron bath and is collected in a slag which covers and insulates the top of the bath. In view of the beneficial insulating function, a slag is always utilized to cover the bath. Thus, a slag is present whether or not a desulphurization process is conducted. However, higher slag volumes are necessarily involved if the pig iron has been desulphurized.
Upon arrival at the steelmaking facility, the contents of the torpedo car are transferred to a transfer ladle for charging into the steelmaking furnace. To effect removal of the contents from the torpedo car, the car is rotated so that the pouring hole or opening in the top of this torpedo-shaped refractory-lined railroad car is positioned in such a manner that the metal and slag flow from the car into the ladle. Prior to this invention, the torpedo cars could not be completely emptied of their contents for various reasons. Typically on the order of 5% of the contents would remain in the car. When attempts were made to remove the final 5%, metal would strike the top of the ladle thereby corroding the rim of the ladle. Striking the rim also causes a safety problem due to spraying of the debris. Such spraying commonly could extend to the weight scales commonly weigh scales are located at the pour station, thereby causing damage to the scales and other equipment.
Failure to remove all of the contents of the torpedo car causes a solidified build-up in the car and, in any event, involves a lowered transport capacity for the vessel. Additionally, slag remaining in the vessel normally has a high sulphur content and thereby serves to contaminate the next load of pig iron from the blast furnace.
To overcome the above mentioned problems associated with lack of complete removal of the contents of the torpedo car, the cars have been emptied at a kish station. Dekishing of the car involves removal of the iron and/or slag remaining in the car. Typically the car is rotated and rerotated until the residual slag and iron materials are essentially completely removed. The iron and slag is normally collected in a pit or on the ground. The accumulated material is then broken and hauled away. Dekishing is a dirty and relatively dangerous operation due to the possibility of an explosion in the event of moisture present in the pit or on the ground. Hence, the elimination of such operation is a highly advantageous objective from the standpoints of safety and environmental control. This invention eliminates the need for dekishing by providing a unique and high advantageous technique whereby virtually the entire contents of the torpedo car can be safely and efficiently transferred into the transfer ladle in the steelmaking facility.